CD133 antigen also known as prominin-1 is a glycoprotein that in humans is encoded by the PROM1gene.[1][2] It is a member of pentaspan transmembrane glycoproteins (5-transmembrane, 5-TM), which specifically localize to cellular protrusions. While the precise function of CD133 remains unknown, it has been proposed to act as an organizer of cell membrane topology.[3]

A CD133+ cell population in brain tumors is thought to be a cancer stem cell (CSC) population, which is rare, undergoes self-renewal and differentiation, and can propagate tumors when injected into immune-compromised mice.[7][10][11] However, subsequent studies have indicated the difficulty in isolating pure CSC populations.[12] CD133+melanoma cells are considered a subpopulation of CSC a critical role in recurrence. Moreover, CD133+ melanoma cells are immunogenic and can be used as an antimelanoma vaccination. In mice the vaccination with CD133+ melanoma cells mediated strong anti-tumor activity that resulted in the eradication of parental melanoma cells.[13] In addition, it has also been shown that CD133+ melanoma cells preferentially express the RNA helicase DDX3X . As DDX3X also is an immunogenic protein, the same anti-melanoma vaccination strategy can be employed to give therapeutic antitumor immunity in mice.[14]